(1) Field of the Invention
The present invention relates to a method for preparing epichlorohydrins from allyl chlorides and an alkyl hydroperoxide.
(2) Description of the Prior Art
As manufacturing techniques of epichlorohydrins, there are known a chlorohydrin process, a chlorination process of allyl alcohol and a peroxide process.
In the chlorohydrin process, allyl chloride and chlorohydrin are used as a raw material and as an oxidizing agent, respectively, and therefore the amount of chlorine which is used therein is too great. In the allyl alcohol process mentioned above, a raw material is expensive. With regard to the aforesaid peroxide process, some manners are known in which tert-butyl hydroperoxide, ethylbenzene hydroperoxide, cumene hydroperoxide, hydrogen peroxide, a peracid and the like are used as oxidizing agents. In addition, there is a process of using a homogeneous catalyst, which is disclosed in Japanase Pat. Publication Nos. 19609/73 and 17649/70 and Tr. Mosk. Khim. Tekhnol. Inst., 74, p. 19-20 (1973). However, this process has the disadvantage that the recovery of the product is intricate and difficult, since the used catalyst is dissolved in the reaction product. There is another synthetic technique for epichlorohydrin in which epoxidation of propylene or allyl chloride is carried out with the aid of an alkyl hydroperoxide in the presence of a solid catalyst in order to synthesize the desired epichlorohydrin, and this synthetic technique is described in West German Pat. No. 2,334,315, U.S. Pat. No. 4,021,454 and J. Catalysis, 31, p. 438 (1973). In these publications, the reaction is performed by the use of the catalyst which has been prepared by first impregnating silica gel with titanium tetrachloride and then calcining it at 500.degree. C. or more, preferably at 800.degree. C.
In these publications, the reaction is performed by using stable tert-butyl hydroperoxide as the hydroperoxide and 2,6-di-tert-butyl-4-methylphenol as a stabilizer, so that epichlorohydrin is obtained in a selectivity of 73% (on the basis of the hydroperoxide). However, when ethylbenzene hydroperoxide is used, the selectivity is 55%, and in the case of the use of cumene hydroperoxide, the selectivity is no more than 8%. Therefore, it is difficult to manufacture epichlorohydrin on an industrial scale by these methods.
There has not been known the technique in which economically advantageous tert-butyl hydroperoxide, ethylbenzene hydroperoxide, cumene hydroperoxide or cyclohexyl hydroperoxide is used as an alkyl hydroperoxide in the presence of a heterogeneous solid catalyst without adding any antioxidant in order to epoxidize allyl chlorides, thereby producing epichlorohydrins in high selectivity.
In the above publications, the following is described: In allyl chlorides, the reactivity of a double bond is noticeably poor because of a high electron attractive force of a chlorine atom, so that the epoxidation reaction scarcely progresses, which results in useless decomposition of the hydroperoxide.